Device for converting rotary motion to axial motion and a method of applying the device for truing, polishing or calibrating a body of rotation

Abstract

This invention concerns an apparatus for the conversion of a rotary motion into an axial motion, said apparatus comprising a number of rolling bearings having larger inner diameter than the outer diameter of a shaft, which extends through the bearings in such a manner that the bearings exert radial forces on the shaft, the vectorial sum of said forces being equal to zero. Each bearing is supported in a recess in one of two or more jaws, said recesses being arranged so that the axis of each bearing is inclined relatively to the axis of the shaft in such a way that each bearing will roll along a helical line on the surface of the shaft. The jaws are totated in common and the jaws are provided with clamping means adapted for increasing the radial forces against the shaft in response to the axial load on the shaft.

What I claim is: 
     
       1. A device for converting rotary motion into axial motion and consisting in a friction unit comprising ball bearings of larger internal diameter than the external diameter of a shaft extending through the inner bearing rings, said ball bearings being so disposed that their inner rings exert radial forces on the shaft, the vector sum of which is substantially nought, the ball bearings being inclined with respect to the shaft axis and wherein the friction unit comprises at least two ball bearing jaws in a retaining member adapted to produce relative rotation between the shaft and the ball bearing jaws, each of which is provided with recesses for supporting the outer ring of at least one ball bearing, said recesses being so inclined that the axis of each ball bearing forms an angle with the plane defined by the shaft axis and the abutment of the inner ring of the said ball bearing against the shaft, the friction unit being further provided with clamping means adapted to clamp the ball bearing jaws more tightly against the shaft in response to an increase of the axial load on the shaft. 
     
     
       2. A device as defined in claim 1, and wherein the clamping members are adapted to clamp the bearing jaws more tightly against each other in response to a relative axial displacement of the jaws caused by an increased axial load on the shaft, each jaw having further spaces in which the ball bearings supported in the other jaw or jaws are freely movable. 
     
     
       3. A device as defined in claim 2, and wherein said clamping members are rigid guide means engaging the jaws in a manner by which a relative axial displacement of the jaws will impart pivoted movement to the guide means. 
     
     
       4. A device as defined in claim 3, and wherein said guide means consist in at least one ring which encloses the jaws and is provided with opposed cams directed and pressing against the outer surface of the jaws. 
     
     
       5. A device as defined in claim 4, characterized in that the said cams are tempered steel balls. 
     
     
       6. A device as defined in claim 2, characterized in that the clamping means are elastic members connecting the jaws. 
     
     
       7. A device as defined in claim 6, characterized in that the elastic means are at least one filament or wire wound around the jaws. 
     
     
       8. A device as defined in claim 7 and comprising two ball bearing jaws arranged substantially symmetrically one on each side of a first axial plane of the shaft, the retaining member comprising two end stops, one arranged to arrest the axial movement of one jaw when the shaft moves in one direction and the other arranged to arrest the axial movement of the other jaw when the shaft moves in the opposite direction. 
     
     
       9. A device as defined in claim 8, and wherein the two end stops are staggered to the same side of a second axial plane perpendicularly disposed to the said first axial plane. 
     
     
       10. A device as defined in claim 1, characterized in that one of the jaws is retained against movement in the axial direction of the shaft. 
     
     
       11. A device as defined in claim 2 and comprising two jaws, each jaw being guided by a carrier member each end of which is slidably supported in the retaining member in a manner which prevents pivotal movement, and each carrier member having at least at one end guide faces cooperating with guiding surfaces of the jaw and comprising two faces which are inclined with respect to the axial direction of the shaft, one forming an angle to one side of the said axial direction, the other an angle to the other side of the axial direction, the carrier members of the two jaws being disposed opposite each other and pressure springs being provided between the retaining member and the said one end of each jaw. 
     
     
       12. A device as defined in claim 11, and wherein each of the said springs rests on an abutment in the retaining member, this abutment being adjustable in the axial direction of the shaft. 
     
     
       13. A device as defined in claim 11, and wherein said guide faces comprise two parts forming different sized angles with the said axial direction and that the guide face part forming the larger angle is located outermost at the end of the carrier member where the said springs are provided. 
     
     
       14. A device as defined in claim 1, and wherein the clamping means are adapted to clamp the jaws more tightly against the shaft in response to an increase of the axial load thereof substantially without relative axial displacement of the jaws. 
     
     
       15. A device as defined in claim 14, and wherein the clamping means comprise a rigid ring enclosing the ball bearing jaws and adapted to exert pressure on the shaft in response to a common displacement of the jaws in the direction of load caused and determined by the axial load on the shaft. 
     
     
       16. A device as defined in claim 15 and having two ball bearing jaws disposed substantially symmetrically on either side of an axial plane of the shaft, the extent of said rigid ring in the axial direction of the shaft being a fraction of the length of the ball bearing jaws, the ring mounted with its axis coincident with the shaft axis when the device in unloaded and secured to each jaw by means of a pair of journals disposed diametrically in the ring and extending into holes flush therewith in the ball bearing jaws the parallel axes of the two pairs of journals extending closely adjacent to the said axial plane of the shaft at a predetermined distance, the retaining member having two abutments disposed so that the ring, irrespective of the direction of the axial load on the shaft, will tilt to the same side and thus urge the jaws against the shaft when it is loaded in axial direction. 
     
     
       17. A device as defined in claim 16, and wherein at least one of said abutments is adjustable in the axial directions of the shaft. 
     
     
       18. A device as defined in claim 15 and having two ball bearing jaws disposed substantially symmetrically on either side of an axial plane of the shaft, the extent of the ring and the ball bearing jaws in axial direction being substantially the same and that for each ball bearing jaw there is provided a pair of recesses which are symmetrical with respect to a plane through the shaft axis and perpendicular to the said axial plane of the shaft, one recess of a pair being provided in the inner surface of the ring and the other recess of the pair provided in the outer surface of the corresponding ball bearing jaw, the bottom of at least one of a pair of recesses forming an angle different from nought with the shaft axis for cooperation with the corresponding inclined face of a wedgeshaped carrier member, said carrier members being supported in a radial groove in the end walls of the retaining member so that the heavy ends of the two wedges face opposed walls of the retaining member. 
     
     
       19. A device as defined in claim 18, and wherein antifriction means are disposed between the cooperating surfaces of the recesses and the carrier member. 
     
     
       20. A device as defined in claim 19, and wherein the antifriction means are tempered steel rolls. 
     
     
       21. A device as defined in claim 18, and wherein the carrier members are adjustable in the axial directions of the shaft. 
     
     
       22. A device as defined in claim 15 and having two ball bearing jaws disposed one on each side of a first axial plane of the shaft, one of the jaws being rigidly connected to said rigid ring while the side of the other jaw facing away from the shaft has a recess extending parallel to the shaft and symmetrical with respect to a second axial plane through the shaft axis and perpendicular to the said first axial plane, the siad recess being aligned with a recess in the inner surface of the ring so as to form on either side of a carrier member extending through the recesses and supported in grooves in opposed walls of the retaining member two channels extending in the direction of the shaft, the width of at least one channel measured perpendicular to the shaft varying periodically in the direction of the shaft, and means attached to the ring for retaining the ball bearing jaws against axial displacement relatively to the ring. 
     
     
       23. A device as defined in claim 22, and wherein the width of one channel varies periodically and the width of the other channel is constant. 
     
     
       24. A device as defined in claim 22, and wherein at least one channel contains tempered steel rolls. 
     
     
       25. A device as defined in claim 14, having two ball bearing jaws retained against relative axial displacement, means being provided between one ball bearing jaw and a carrier member to prevent rotation but to permit axial displacement of the ball bearing jaw relatively to the carrier member, the ends of said carrier member being supported in radial grooves in opposed end walls of the retaining member, clamping means being further provided to clamp the jaws together in response to their axial displacement in relation to the carrier member. 
     
     
       26. A device as defined in claim 25, and wherein said means provided between one ball bearing jaw and the carrier member are tempered steel balls disposed in opposed axial grooves in respectively the ball bearing jaw and the carrier member. 
     
     
       27. A device as defined in claim 14, and wherein said clamping means are at least one elastic wire or filament wound around the carrier member and the second ball bearing jaw. 
     
     
       28. A device as defined in claim 1, and wherein the inner surface of the inner ring of each ball bearing in cross-section has a convexity facing the shaft such that the said surface contacts the surface of the shaft along a generating line for the shaft surface over substantially the entire width of the ball bearing. 
     
     
       29. A device as defined in claim 1, and wherein the inner surface of the inner ring of each ball bearing exhibits a plurality of elevations of substantially arched cross-section and disposed side by side. 
     
     
       30. A method of truing, polishing or calibrating a body of revolution, specifically a cylindrical shaft, said treatment being carried out by passing the body of revolution through a friction unit comprising at least two ball bearing jaws in a retaining member adapted to produce relative rotation between the shaft and the ball bearing jaws, each of which is provided with recesses for supporting the outer ring of at least one ball bearing, said recesses being so inclined that the axis of each ball bearing forms an angle with the plane defined by the shaft axis and the abutment of the inner ring of the said ball bearing against the shaft, the friction unit being further provided with clamping means adapted to clamp the ball bearing jaws more tightly against the shaft in response to an increase of the axial load on the shaft. 
     
     
       31. A method as defined in claim 30, and whereby a friction device is used in which the ball bearings are so inclined in the jaws that the respective inner rings move on the body of revolution along helical lines having the same pitch. 
     
     
       32. A method as defined in claim 31, and whereby a friction device is used in which at least one ball bearing is so mounted in the device that its inner ring, if it were operated alone, would move on the body of revolution along a helical line having a pitch different from that of at least one of the other ball bearings. 
     
     
       33. A method as defined in claim 30, and whereby a friction device is used in which the retaining member is held against movement.